JPH0550713U - Transformer - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A small transformer with low noise and loss is obtained by providing a slit hole in the core that extends in the direction intersecting the magnetic path. [Structure] Iron core legs 2u, 2v, 2w or yoke 1
Each of a and 1b is provided with one or a plurality of slit holes 6 so as to extend at a predetermined angle with respect to the magnetic flux flowing direction.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a transformer, and more particularly to a transformer effective for use in a power conversion device.

[0002]

[Prior Art]

 The PWM method is generally used as a method for obtaining alternating current from direct current. In this PWM method, the AC output voltage contains some DC component. This direct current component is caused by variations in the forward voltage drop (VF characteristic) of the semiconductor element, variations in dead time for preventing a short circuit between the upper and lower arms, or variations in the voltage of the direct current line. In an inverter that employs the PWM method, if there is a transformer (commonly called an inverter transformer) in the AC output line, the transformer core is saturated due to this DC component, and the AC output current of the inverter suddenly increases. May increase or the output voltage on the secondary side of the transformer may decrease, causing the output voltage to fluctuate.

At present, in order to prevent the magnetic bias of the inverter transformer due to this DC component, a current detector capable of measuring the DC component is attached to the AC output line, and the DC current component of the AC line is detected. Feedback control is applied so as to decrease.

That is, FIG. 10 shows a DC bias prevention apparatus of a conventional constant voltage constant frequency power supply (CVCF apparatus). In the figure, 1 is a DC power source, 2a to 2d are semiconductor switch elements, 3 is an output transformer, 4 is a coil, 5 is a capacitor, and an AC filter circuit 6 is formed by these coils 4 and a capacitor 5, and a DC power source. 1, the semiconductor switch elements 2a to 2d, the output transformer 3 and the AC filter circuit 6 constitute a main circuit. In the CVCF having such a main circuit configuration, the output voltage is detected by the voltage transformer 7, the detected voltage is rectified by the rectifier 8, and this voltage value is compared with the set voltage value Vset by the matching circuit 9 and amplified. The error is amplified by the circuit 10, and the output of the reference sine wave generator 11 is multiplied by the multiplier 12. The output of the multiplier 12 and the output of the triangular wave generator 13 are compared in magnitude by a comparator 14 to generate control signals Sa to Sd. Further, the primary current of the output transformer 3 is detected by the current transformer 15, and the detected current is passed through the low-pass filter 16 to detect the direct current component, and this value is compared with the set current value Iset, and the amplification circuit The error component 17 is used for error amplification, and the matching circuit 18 biases the output of the multiplier 12 to control the DC component of the output transformer 3. Although FIG. 2 shows a CVCF having a single-phase output, it can be similarly applied to a CVCF having a three-phase output.

In the transformer used in the above power converter, in order to downsize the device and reduce the loss, the core is made of grain-oriented silicon steel sheet and the magnetic flux density is increased to about the same level as that of the commercial transformer. The exciting current of the transformer using the grain-oriented silicon steel plate is small, and the iron plate saturation magnetic flux density of 2.1T tends to rapidly increase from about 1.9T. Although there is a tendency to use the above-mentioned transformer, due to such iron plate characteristics, the iron core is easily saturated by a slight DC current. When the iron core magnetic flux density exceeds 1.9T, the problem that the output voltage is not stable due to the non-linear characteristic that the exciting current increases rapidly and the overcurrent phenomenon due to the rapid increase of the exciting current occur (Fig. Shown in).

Conventionally, in order to avoid such a phenomenon, the structure shown in FIGS. 6 and 7 is used. That is, in FIGS. 6 and 7, 1a and 1b are yokes, 2u, 2v and 2w are leg portions formed between the yokes 1a and 1b, and 3a to 3c are substantially central portions of the leg portions 2u to 2w. Gaps 4a to 4c are provided between the yoke 1a and the legs 2u to 2w, and 5a to 5c are gaps provided between the legs 2u to 2w and the yoke 1b. Were provided in an appropriate combination. As a result, the exciting current is increased to 10 to 20% of the rated current, the magnetic flux density of the iron core is set to about 1.0 turn (1T), and a transformer structure that does not cause DC bias to the expected DC voltage component is provided. I was there.

[0007]

[Problems to be solved by the device]

 In the transformer as shown in FIGS. 6 and 7, the core excitation characteristics are obtained as shown in FIGS. 8 and 9, and the characteristics are improved to some extent. However, such a transformer has drawbacks such as large size and loss, and increased noise due to the gap between the yoke and the leg.

The present invention has been made in view of the above problems, and an object thereof is to provide a small-sized transformer with small noise and loss by providing a slit hole extending in a direction intersecting with a magnetic path in an iron core portion. It is to be.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a transformer having an iron core composed of a yoke and legs, wherein the iron core is provided with a slit hole having a predetermined angle with respect to a magnetic path formed in the iron core. It is characterized in that it is configured.

[0010]

[Action]

 As the iron core magnetic flux density increases, the equivalent equivalent of the gap becomes larger, and a sudden increase in the exciting current is prevented.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a front view of a transformer according to a first embodiment of the present invention, FIG. 2 is a side view thereof, and the same or corresponding parts as those of FIGS. 6 and 7 are designated by the same reference numerals. .. In this embodiment, as shown in FIGS. 1 and 2, the leg portions 2u to 2w each have a slit-shaped hole extending in a direction substantially orthogonal to the magnetic path formed when the transformer is excited. 6 are provided.

By providing the holes 6 in the transformer having the above structure, the iron core gap is equivalently increased as the iron core magnetic flux density is increased.

Specifically, the average magnetic flux density of the cross section P-Q is set to about 1.6T, and the average magnetic flux density of the cross section P'-Q 'at this time is set to about 1.9T. If there is no direct current component, the exciting current of the iron core is small. If a direct current is generated and the iron core is demagnetized by about 0.2T, the average magnetic flux density of the cross section P-Q is about 1.8T at maximum, but the average magnetic flux density of the cross section P'-Q 'is 2.1T. Becomes saturated. This is the same as when a gap was created equivalently in the iron core, and the exciting current increases. Further demagnetization increases the saturation region of the slit, which is equivalent to increasing the gap length.

In a transformer without slits, when the DC bias is magnetized, the entire iron core saturates, which causes a rapid increase in the exciting current. However, in transformers with slits, only the slits are saturated and those without slits Since is not saturated, there is no sudden increase in exciting current. Fig. 5 shows the excitation characteristics of the inverter transformer with slits. As a result, stable control can be realized.

As described above, according to this embodiment, by slitting the core legs of the inverter transformer, (1) the magnetic flux density of the iron core of the inverter transformer can be increased. Low loss can be achieved. (2) Since it is not necessary to provide a gap between the conventional yoke and legs, it is possible to reduce noise. (3) DC bias magnetism can be stably controlled, and it is possible to eliminate the overcurrent of the inverter AC line and the fluctuation of the output voltage that have been conventionally generated.

3 and 4 show a transformer according to a second embodiment of the present invention. In this embodiment, the magnetic paths of the yokes 1a and 1b are formed at the portions where the magnetic paths are formed. A slit hole 7 extending in a substantially orthogonal direction is formed, and the same action and effect as those of FIGS. 1 and 2 can be obtained.

[0018]

[Effect of the device]

 The present invention is as described above, and one or more slit holes are provided in the iron core leg or the yoke so as to extend at a predetermined angle with respect to the magnetic flux flowing direction. When used as an output transformer of an inverter, its excitation characteristics can suppress the rapid increase of the excitation current due to the saturation of the iron core with respect to the direct current component generated by the inverter, making it compact and reducing noise and loss. A reduced transformer is obtained.

[Brief description of drawings]

FIG. 1 is a front view of a transformer according to a first embodiment of the present invention.

2 is a side view of the transformer of FIG. 1. FIG.

FIG. 3 is a front view of a transformer according to a second embodiment of the present invention.

4 is a side view of the transformer of FIG.

FIG. 5 is an iron core excitation characteristic diagram of a transformer according to an embodiment of the present invention.

FIG. 6 is a front view of a conventional transformer.

7 is a side view of the transformer of FIG.

FIG. 8 is an iron core excitation characteristic diagram of a conventional transformer.

FIG. 9 is an iron core excitation characteristic diagram of a conventional transformer.

FIG. 10 is a block diagram of a control device of the power conversion device.

[Explanation of symbols]

1a, 1b ... Yoke, 2u, 2v, 2w ... Iron core leg, 6,
7 ... Slit hole.

Claims (1)

[Scope of utility model registration request] 1. A transformer provided with an iron core composed of a yoke and legs, wherein the iron core is provided with slit holes having a predetermined angle with respect to a magnetic path formed in the iron core. vessel.